Shape-memory materials have the ability to change from a permanent or desired shape into a temporary transitional shape and then back into the permanent or desired shape. Shape-memory materials are stimuli-responsive in that they can change shape upon application of an external stimulus. These solid materials are initially formed into a “permanent” shape or configuration suited for their ultimate use. These materials can then be transformed into a transitional shape to facilitate, for example, implantation. Once implanted, an external stimulus (e.g., heat, light, chemical) can be applied to the material to transform the material back into its permanent shape or configuration. This process involves “programming” the shape-memory polymer from its permanent shape into a temporary shape and then “recovering” the permanent shape from the temporary shape.
In view of the advantages such materials provide, medical device implants are increasingly made with shape-memory materials. Typically, shape-memory materials are used so the implant can be temporarily reduced in size, thus requiring a smaller surgical entry site, and in the case of bone implants, smaller drilled holes in the bone. Smaller surgical entry sites and drilled holes lessen the invasiveness of the procedure and shorten recovery time.
When mass producing medical device implants made with shape-memory materials, a programming process should be conducted such that the devices are uniformly produced in their temporary shape without adversely affecting the devices' ability to transition back from the temporary shape to the permanent shape.